A passive optical network (PON) uses a point-to-multipoint architecture to couple an optical line terminal (OLT) with multiple optical network units (ONUs). To implement the point-to-multipoint architecture, a single optical fiber that is connected with the OLT on one end is split into multiple connections on the other end for the ONUs. The bandwidth of the fiber is shared between all of the ONUs that are connected to the fiber. When the OLT transmits data downstream through the fiber, the data is received by every ONU that is connected to the fiber. If a particular ONU receives data that is not intended for that ONU, the data is discarded.
The amount of energy that is consumed by an ONU is directly related to the speed at which data can be processed by the ONU. Because the time-based statistics of downstream traffic destined to a particular ONU cannot be assured, present ONUs must contain large buffer memories, capable of absorbing large downstream transmissions at the full PON line rate until such time as the data can be played out on subscriber interfaces, which typically operate at much lower speeds. These large buffer memories consume an appreciable amount of power.
One proposed technology for conserving energy in an ONU is commonly referred to as bit interleaving passive optical network (BIPON). In a BIPON, an ONU samples only certain bits of the downstream data that is received by the ONU. The bits that are sampled correspond to data that is intended for the ONU, while the rest of the downstream data that is not intended for the ONU can be discarded without sampling, thereby conserving energy by reducing the required size or speed of the buffer memory further downstream in the flow.